Shiva Purana
तृतीयावरणे चक्रुः पूर्वभागे समर्चयेत् ॥ नारायणाख्यां याम्येस्त्रं क्वचिदव्याहतं यजेत् ॥ ५९ ॥
On the third covering, one should worship the Chakra in the eastern part. One should sometimes worship the Yamya weapon known as Nārāyaṇa without interruption.
english translation
tRtIyAvaraNe cakruH pUrvabhAge samarcayet ॥ nArAyaNAkhyAM yAmyestraM kvacidavyAhataM yajet ॥ 59 ॥
hk transliteration by Sanscript